The use of hair dyes is widespread. It’s estimated that more than a third of women over age 18 and 10 percent of men over age 40 – a group that numbers in the millions in the U.S. alone – color their hair. Even if exposure to hair dye increases cancer risk only slightly, the effect on public health could be significant.
We turned to the National Cancer Institute (NCI) to investigate.
In the 1970s, hair dye manufacturers removed some chemicals in their products that were found to cause cancer in animals, the NCI’s website reports. But concerns about a possible link between dyes and cancer have persisted.
Relatively few research studies have looked for an association between hair dyes and cancer, and in those, the results are inconclusive, according to the NCI. Some studies have linked dyes with an increased risk of certain blood cancers, such as non-Hodgkin lymphoma and leukemia, while others have found no such connection. Studies of a suspected link between hair dyes and breast and bladder cancer have likewise produced conflicting results.
After reviewing the evidence, the International Agency for Research on Cancer reported in 2008 that personal use of hair dyes is “not classifiable as to its carcinogenicity [cancer-causing potential] to humans.”